Radial head prosthesis with floating articular member

ABSTRACT

System, including apparatus, methods, and kits, for replacement of the proximal end of a radial bone with a prosthesis having a floating articular member. The prosthesis may include a head portion connected or connectable to a stem portion. While the stem portion remains operatively connected to the head portion, the head portion and/or an articular member thereof may be permitted to float in position relative to the stem portion. The head portion/articular member may float transversely (e.g., translationally) and/or rotationally with respect to the stem portion. The articular member may articulate with a humeral bone or both a humeral bone and an ulnar bone. In some embodiments, the head portion may include a fixed member for articulation with an ulnar bone and a floating member for articulation with a humeral bone.

CROSS-REFERENCE TO PRIORITY APPLICATION

This application is based upon and claims the benefit under 35 U.S.C.§119(e) of U.S. Provisional Patent Application Ser. No. 61/699,070,filed Sep. 10, 2012, which is incorporated herein by reference in itsentirety for all purposes.

INTRODUCTION

The human elbow joint is formed at the junction of the humerus, radius,and ulna. In this compound joint, the proximal head of the radius, or“radial head,” articulates at its end with the capitellum of thehumerus, to form the humeroradial joint, and on its side with the radialnotch of the ulna, to form the proximal radioulnar joint. The radialhead thus provides two articular surface regions in the elbow joint: (1)a concave, generally spherical end surface region for articulation withthe capitellum, and (2) a convex, roughly cylindrical, side surfaceregion for articulation with the radial notch.

The end and side of the radial head permit the radius to achievedistinct motions when the arm is flexed and extended, relative to whenthe hand is pronated and supinated. During flexion and extension, theend of the radial head moves on the curved surface of the capitellum,with the humeroradial joint functioning as a hinge joint. In contrast,when the hand is rotated to change its pronation-supination position,the end of the radial head pivots on the capitellum, and the side of theradial head turns in the radial notch.

Trauma to the elbow joint frequently involves damage to the ligamentoussupport of the elbow and the elbow's osseous structures. The radial headoften is fractured either in isolation or in combination with otherinjuries to the bony or ligamentous structures of the joint; suchfractures can be reconstructable or unreconstructable. In general,unreconstructable radial head fractures result from high-energy traumaand therefore frequently are associated with significant injuries toother aspects of the elbow. In such cases, restoration of thestabilizing function of the radial head is crucial to allowing theligamentous damage and other injuries to heal properly. To achieve this,prosthetic replacement of the entire radial head has become relativelycommon.

A radial head prosthesis can be fashioned from a single piece of metal,often an alloy including cobalt and chromium (“cobalt-chrome”).Alternatively, to overcome various problems associated with theinsertion and removal of such one-piece devices, modular radial headprostheses have been developed that can be assembled during surgery. Inany event, the prosthesis generally includes a stem and a head. The stemis received in a medullary cavity of the radius. The head may be shapedto approximate the natural anatomy of the radial head. In particular,the head provides an end surface region and a side surface region, whichare artificial replacement surfaces corresponding to the naturalarticular surfaces described above.

A shortcoming of radial head prostheses in the prior art is thedifficulty of accurately positioning both the end and side articularsurfaces of the prosthesis for proper articulation with the capitellumand radial notch, respectively.

SUMMARY

The present disclosure provides a system, including apparatus, methods,and kits, for replacement of the proximal end of a radial bone with aprosthesis having a floating articular member. The prosthesis mayinclude a head portion connected or connectable to a stem portion. Whilethe stem portion remains operatively connected to the head portion, thehead portion and/or an articular member thereof may be permitted tofloat in position relative to the stem portion. The headportion/articular member may float transversely (e.g., translationally)and/or rotationally with respect to the stem portion. The articularmember may articulate with a humeral bone or both a humeral bone and anulnar bone. In some embodiments, the head portion may include a fixedmember for articulation with an ulnar bone and a floating member forarticulation with a humeral bone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an anterior view of a right elbow joint including a firstembodiment of an exemplary radial head prosthesis having a head portionthat includes a floating, self-centering articular member structured asa dish member for articulation with the capitellum of the humerus, withthe prosthesis mounted to the radius such that the head portion replacesthe natural radial head, in accordance with aspects of the presentdisclosure.

FIG. 2 is a side view of the prosthesis of FIG. 1, taken at elevation inthe absence of bone.

FIG. 3 is another view of the prosthesis of FIG. 1, taken from generallyabove the prosthesis.

FIG. 4 is a fragmentary, exploded side view of the prosthesis of FIG. 1.

FIG. 5 is a side view of selected components of the prosthesis of FIG.1, particularly the dish member and a retainer that attaches the dishmember to a fixed cup member of the head portion.

FIG. 6 is a fragmentary sectional view of the prosthesis of FIG. 1,taken generally along line 6-6 of FIG. 2.

FIG. 7 is a sectional view of the cup member of the prosthesis of FIG.1, taken generally as in FIG. 6 but in isolation from other prosthesiscomponents.

FIG. 8 is a top view of the cup member of FIG. 7, taken generally alongline 8-8 of FIG. 7.

FIG. 9 is a top view of one of the retainer components of the prosthesisof FIG. 1, taken generally along line 9-9 of FIG. 4.

FIG. 10A is inner side view of the retainer component of FIG. 9, takengenerally along line 10A-10A of FIG. 9.

FIG. 10B is an outer side view of the retainer component of FIG. 9,taken generally along line 10B-10B of FIG. 9.

FIG. 11 is a top view of the dish member of the prosthesis of FIG. 1.

FIG. 12 is a bottom view of the dish member of the prosthesis of FIG. 1.

FIG. 13 is a view of selected components of an exemplary elbow repairsystem, in accordance with aspects of the present disclosure.

FIG. 14 is a sectional view of a second embodiment of a radial headprosthesis having a floating dish member for engagement with thecapitellum, taken generally as in FIG. 6 but with only the head portionvisible and with the dish member having a biased position produced by abiasing member, in accordance with aspects of the present disclosure.

FIG. 15 is a sectional view of a third embodiment of a radial headprosthesis having a floating dish member for engagement with thecapitellum, taken generally as in FIG. 6 but with only the head portionvisible and with the dish member having a biased position produced by abiasing member, in accordance with aspects of the present disclosure.

FIG. 16 is a fragmentary sectional view of a fourth embodiment of aradial head prosthesis having a floating articular member, takengenerally as in FIG. 6, with the articular member captured by a retainerthat is at least partially resilient, which may provide ashock-absorbing and/or biasing function, in accordance with aspects ofthe present disclosure.

FIG. 17 is a sectional view of a fifth embodiment of a radial headprosthesis having a floating articular member, with the articular memberbeing an inverted cup member that articulates with the ulna and thehumerus, in accordance with aspects of the present disclosure.

FIG. 18A is a sectional view of a sixth embodiment of a radial headprosthesis having a floating articular member forming at least part ofthe head portion, with the head portion being rotatably connected to astem portion and with at least one resilient member disposed between thehead portion and the stem portion, in accordance with aspects of thepresent disclosure.

FIG. 18B is a sectional view of a seventh embodiment of a radial headprosthesis having a floating articular member forming at least part ofthe head portion, with the head portion being rotatably connected to astem portion as in FIG. 18A and with a resilient ring replacing theresilient members of FIG. 18A, in accordance with aspects of the presentdisclosure.

FIG. 19 is a fragmentary sectional view of an eighth embodiment of aradial head prosthesis having a floating articular member forming atleast part of the head portion, with the floating articular memberincluding a pivotable joint that allows rotational motion of an upperregion of the articular member, in accordance with aspects of thepresent disclosure.

FIG. 20 is a sectional view of a ninth embodiment of a radial headprosthesis having a floating articular member, with the articular memberhaving a convex bottom surface that is slidably engaged with a concavefloor region of a cup member, in accordance with aspects of the presentdisclosure.

FIG. 21 is a fragmentary sectional view of a tenth embodiment of aradial head prosthesis having a floating articular member, with thearticular member having a flat bottom surface that is slidably engagedwith a flat floor region of a cup member, in accordance with aspects ofthe present disclosure.

FIG. 22 is a fragmentary sectional view of an eleventh embodiment of aradial head prosthesis having a floating articular member, with thearticular member having a curved and concave (e.g., spherical) surfaceregion that is slidably engaged with a complementary floor region of acup member, in accordance with aspects of the present disclosure.

FIG. 23 is an exploded side view of a twelfth embodiment of a radialhead prosthesis having a floating articular member, with a base regionof the articular member being received transversely in a hollow body ofthe head portion, in accordance with aspects of the present disclosure.

FIG. 24 is an exploded sectional view of a thirteenth embodiment of aradial head prosthesis having a floating articular member, with thearticular member being retained with a clip in a cup member, inaccordance with aspects of the present disclosure.

FIG. 25 is a sectional view of the prosthesis of FIG. 24, takengenerally along line 25-25 of FIG. 24 through the floating articularmember and clip.

FIG. 26 is a fragmentary sectional view of a fourteenth embodiment of aradial head prosthesis having a floating articular member, with thearticular member being retained in a cup member with a pin, inaccordance with aspects of the present disclosure.

FIG. 27 is a side view of the articular member of FIG. 26, taken towarda slot that receives a leading end of the pin.

FIG. 28 is an exploded sectional view of a fifteenth embodiment of aradial head prosthesis having a floating articular member, with thearticular member being structured as an inverted cup member held on asupport member by a snap-in retainer received in the cup member frombelow the support member, in accordance with aspects of the presentdisclosure.

FIG. 29 is a fragmentary sectional view of a sixteenth embodiment of aradial head prosthesis having a floating articular member, in accordancewith aspects of the present disclosure.

FIG. 30 is a fragmentary sectional view of a seventeenth embodiment of aradial head prosthesis having a floating articular member, with thearticular member being structured as an inverted cup member held on asupport member by a clip received in a circumferential groove defined bythe cup member, in accordance with aspects of the present disclosure.

FIG. 31 is a fragmentary sectional view of an eighteenth embodiment of aradial head prosthesis having a floating articular member, in accordancewith aspects of the present disclosure.

DETAILED DESCRIPTION

The present disclosure provides a system, including apparatus, methods,and kits, for replacement of the proximal end of a radial bone with aprosthesis having a floating articular member. The prosthesis mayinclude a head portion connected or connectable to a stem portion. Whilethe stem portion remains operatively connected to the head portion, thehead portion and/or an articular member thereof may be permitted tofloat in position relative to the stem portion. The headportion/articular member may float transversely (e.g., translationally)and/or rotationally with respect to the stem portion. The articularmember may articulate with a humeral bone or both a humeral bone and anulnar bone. In some embodiments, the head portion may include a fixedmember for articulation with an ulnar bone and a floating member forarticulation with a humeral bone. In some embodiments, the prosthesismay have at least one resilient member, which may bias a position of thehead portion/articular member relative to the stem portion, cushiontravel of the head portion/articular member, absorb shocks, and/or thelike.

Further aspects of the present disclosure are described in the followingsections: (I) exemplary replacement system for a proximal radial head,(II) prosthesis installation, and (III) examples.

I. Exemplary Replacement System for a Proximal Radial Head

This section describes an exemplary replacement system (interchangeablytermed an elbow repair system) for a proximal head of a radial bone; seeFIGS. 1-13. The system includes an exemplary radial head prosthesishaving an articular member that is configured to float (i.e., have avariable position/orientation) during use and with respect to otherportions of the prosthesis, which may allow the articular member to beself-centering and/or dynamically/automatically adjustable in positionas the radius moves with respect to the adjacent ulna and humerus.

The articular member may be slidable, that is, movable transversely withrespect to a long axis of the prosthesis, when the prosthesis isdisposed in an operative configuration, namely, when a head portion anda stem portion of the prosthesis are operatively connected to oneanother. The prosthesis may have a fixed articulation surface region(and/or articular member) for engagement of an ulnar bone(interchangeably termed an ulna) and a movable articulation surfaceregion (and/or articular member) for engagement of a humeral bone(interchangeably termed a humerus). Each surface region and/or articularmember that articulates with a bone or bone region forms at least partof a movable joint with that bone or bone region. In other cases, theprosthesis may have a head member that moves as a unit with respect tothe stem portion and that articulates with both the ulna and thehumerus. In some embodiments, the floating articular member may becapable of sliding transversely and rotating.

The articular member may articulate with a natural region and/or anartificial region of a bone. For example, if the radial head prosthesisis installed in a hemi-arthroplasty procedure that removes the radialhead but does not remove the associated radial notch or capitellum, thearticular member may articulate with a natural region of an ulnar boneand/or a humeral bone. In other cases, such as when the radial headprosthesis is installed in a total arthroplasty procedure, the articularmember of the prosthesis may articulate, at least in part, with anartificial/implanted region (a prosthetic region) of an ulnar boneand/or a humeral bone.

FIG. 1 shows a right elbow joint including an exemplary radial headprosthesis 50 having a head portion 52 that includes a floatingarticular member, in this case, dish member 54. Prosthesis 50 has a stemportion 56 that mounts the prosthesis and/or head portion 52 to a radialbone 58 (interchangeably termed a radius). In the fully assembledconfiguration of the prosthesis, before or after prosthesis installationin a recipient, the stem portion is operatively connected to the headportion.

Stem portion 56 may include a shaft 60 disposed in a medullary cavity 62of the radius. The shaft may be fixed to the radius, such as via anadhesive, one or more fasteners (e.g., bone screws), an interferencefit, or a combination thereof, among others.

Head portion 52 is structured and positioned to articulate with (orcontact) a humeral bone 64 (interchangeably termed a humerus) and anulnar bone 66 (interchangeably termed an ulna). More particularly, headportion 52 has a top surface region 68 (interchangeably termed an end ortop articular region or contact region) for engagement with capitellum70 of the humerus and a side surface region 72 (interchangeably termed aside articular region or a side wall) for engagement with radial notch74 of the ulna. In the depicted embodiment, top surface region 68 isprovided by floating dish member 54 and side surface region 72 isprovided by a perimeter surface area of a cup member or housing member76 of head portion 52, with the cup member fixed with respect to stemportion 56. The head portion of prosthesis 50 may be described as acompound head (interchangeably termed a composite head) having two ormore discrete components (each formed of one or more discrete pieces)that collectively form the articular surface regions for articulationwith the humerus and ulna.

The medial-lateral distance (the M/L offset) from radial notch 74 to thecenterline of capitellum 70 is roughly fixed during flexion andextension of the arm. Accordingly, the diameter of head portion 52(e.g., cup member 76) may be selected according to the M/L offset(generally, by selection of a diameter that is about twice the M/Loffset), to roughly center head portion 52 under the capitellum in amedial-lateral direction.

The centerline of capitellum 70 may be offset anteriorly (orposteriorly) from the centerline of radial notch 74, to form ananterior-posterior offset (an A/P offset). Thus, the top articularsurface region of head portion 52 may need to be offset correspondinglyin an anterior-posterior direction to center the top articular surfaceregion under the capitellum in an anterior-posterior direction.Furthermore, the size of the capitellum varies, so the curvature of thetop articular surface region of the head portion may be selected tomatch the particular curvature of the recipient's capitellum.

Radial head prostheses of the prior art generally provide an implantwith a fixed shape and size. Accordingly, to accurately match theanatomy of any given recipient in the operating room, a surgeon needs tohave access to a large set of prostheses of different shapes and sizes,to ensure the availability of an implant with a good fit. However, sincehaving a large set of implants is impractical, the surgeon often selectsa prosthesis in the operating room from a smaller set of availableprostheses and settles for an imperfect fit, which may produce bonewear, such as erosion of the capitellum. The prosthesis thus mayfunction poorly, damage bone, and cause pain.

Improved radial head prostheses are needed that offer more flexibilityin selection of a suitable size, shape, and/or position of thereplacement head and/or articular surface regions thereof. Prosthesis 50and other prostheses disclosed herein satisfy the long-felt need formore flexibility in prosthesis selection and positioning. Theseinnovative prostheses may be dynamically positioned and self-centeringduring flexion-extension and pronation-supination movements of theradial bone.

FIGS. 2 and 3 show views of prosthesis 50 in the absence of bone. Theprosthesis may include an intermediate portion or collar portion 80disposed between head portion 52 and stem portion 56. The collar portionmay form a shoulder or stop 82 that engages the prepared end of thetruncated radius, to stop travel of the stem portion into the radius.The collar portion may have a diameter intermediate the diameter of thehead portion and the diameter of the stem portion. The collar portionmay be provided by a head component (of one or more discrete pieces)that forms head portion 52, a stem component (of one or more discretepieces) that forms stem portion 56, by a discrete collar component (ofone or more discrete pieces), or any combination thereof. In some cases,the prosthesis may have no collar portion.

FIG. 4 shows a fragmentary, exploded side view of prosthesis 50. Theprosthesis may include a stem component 84 forming stem portion 56 and,optionally, collar portion 80. The stem component may be attached orattachable to a head component 86 at a connection interface 88. Theconnection interface may, for example, include a projection 90 of headcomponent 86 mated with a complementary recess or socket 92 of the stemcomponent, or vice versa. The connection interface may lock the stemcomponent to the head component. Exemplary connection interfaces mayinclude a tapered recess and a tapered projection (such as afrustoconical taper (e.g., a Morse taper)), a dovetail taper, or thelike.

Head component 86 (interchangeably termed a head assembly) may provideall of head portion 52. The head component may include cup member 76,dish member 54, and a retainer 96 that traps the dish member in the cupmember. The cup member may be described as a fixed articular member thatis fixedly connected to stem portion 56, such that the fixed articularmember has a fixed position with respect to the stem portion duringmovement at the elbow joint (e.g., during movement of the radial bonewith respect to the associated ulna and humerus). The dish member may bedescribed as a floating articular member that is movably connected tothe stem portion, such that the floating articular member is permittedto have a variable position with respect to the stem portion (and/or thefixed articular member) during movement at the elbow joint (e.g., duringmovement of the radial bone with respect to the associated ulna andhumerus). In some cases, a floating articular member may articulate withboth the ulna and the humerus.

Cup member 76 forms side articular surface region 72 for articulationwith the radial notch of the ulna. The cup member defines a recess orcavity 98 (e.g., a cylindrical or frustoconical recess, among others)that receives dish member 54 and retainer 96. The recess may have afloor region 100, which may be flat (planar), convex, or concave. Insome cases, the floor region may be curved and concave (or convex)(e.g., spherical), for example, corresponding to less than one-half of asphere, such as less than about 25% or 10% of a complete sphere. Aretaining flange 102 (interchangeably termed a detent) may be formed inthe cup member around the perimeter of recess 98, such as near thebottom of the recess, as shown, or near or at the top of the recess,among others. (Alternatively, or in addition, at least one detent 102may be formed by the retainer.) The cup member and/or articular surfaceregion 72 may be formed of metal (e.g., cobalt-chrome) and/or polymer,among others. In some cases, a body of the cup member may be formed ofmetal, and recess 98 and/or a portion thereof (such as a lower region orthe floor region) may be covered with a polymer liner.

Dish member 54 has an upper region 104 that provides top articularsurface region 68 for contact with the capitellum. Upper region 104 maybe circular (e.g., at least generally disc-shaped) or oval, amongothers. Top articular surface region 68 may be curved and concave, suchas concave spherically. Upper region 104 may be fixed to a base region106 via a neck region 108. Dish member 54 and/or articular surfaceregion 68 may be formed of metal and/or polymer, among others.

Retainer 96 may be composed of only one component or two or moreretainer components 110. For example, in the depicted embodiment,retainer components 110 define openings 112 sized to collectivelyreceive base region 106 and at least part of neck region 108 of dishmember 54. The retainer may be formed of metal and/or polymer, amongothers. In some cases, the cup member and the dish member may be formedof metal, and the retainer may be formed of plastic. More generally,contacting surface regions within the prosthesis that are slidablyengaged with one another may be metal against metal, plastic againstplastic, or metal against plastic, among others. Furthermore, a pair ofsuch contacting surface regions that movably contact one another bothmay be flat (planar), one concave and the other convex (e.g.,complementary to one another or with different curvatures; see SectionIII), both convex, or the like.

FIG. 5 shows a side view of retainer components 110 positioned aroundbase region 106 and neck region 108 of dish member 54. The arrangementof pieces shown in FIG. 5 may be pressed into cup member 76 (see FIG.4), such that detent 102 of the cup member is received in a groove 114formed by retainer components 110, to prevent removal of the retainer.The retainer components may be sufficiently resilient to allow theretainer to be snapped into the cup member, to prevent removal of theretainer from the cup member. The retainer may be snapped into a fixedconfiguration in the cup member, or the retainer may be movably held inthe cup member.

FIG. 6 shows a fragmentary sectional view of prosthesis 50 in a fullyassembled or operative configuration in which head portion 52 isoperatively connected to stem portion 56. Dish member 54 may be capableof transverse motion, indicated at 120, in directions transverse to along axis 122 defined by stem portion 56 and/or prosthesis 50. Here,dish member 54 is slidable in a plane that is transverse (e.g.,orthogonal) to long axis 122, as indicated by a copy of the dish membershown in phantom outline. More particularly, openings 112 of retainercomponents 110 form a retainer cavity that permits transverse motion(interchangeably termed lateral motion) of base region 106 and neckregion 108 (see FIGS. 4 and 5), while preventing removal of the baseregion from the cavity. As described in more detail below in SectionIII, the dish member (and/or an articular member and/or the headportion) also may capable of rotating about a fixed or variabletransverse axis (e.g., to change the tilt of the dish member/articularmember/head portion), pivotal motion about long axis 122 and/or about ahead axis 124 that is at least generally parallel to long axis 122,and/or motion (e.g., translational motion) along long axis 122 and/orhead axis 124.

Dish member 54 may or may not project above the top of cup member 76.Accordingly, the top of dish member 54 may be approximately flush withthe top of cup member 76, or may end below or extend above the top ofthe cup member by any suitable distance.

FIGS. 7-12 present additional features of prosthesis 50. FIGS. 7 and 8show respective sectional and top views of cup member 76. Detent 102 mayextend partially or completely around recess 98. FIGS. 9, 10A, and 10Bshow various views of one of retainer components 110. FIGS. 11 and 12show respective top and bottom views of dish member 54.

FIG. 13 shows selected components of an exemplary elbow repair system130 for replacement of a natural radial head with a prosthetic head. Thesystem, which may be supplied as a kit, may include at least one dishmember 54 or a set 132 of two or more dish members 54, at least one cupmember 76 or a set 134 of two or more cup members 76, and at least onestem component 84 and/or stem portion 56 or a set of two or more stemcomponents 84 and/or stem portions 56. The system also may include aretainer to connect a dish member to a cup member, one or more trialimplants, instruments to prepare a radial bone, and the like.

Set 132 may be composed of floating articular members or dish members 54with different top articular surface regions 68. The surface regions 68may have different curvatures relative to one another, as shown. Forexample, surface regions 68 may be characterized by different radii ofcurvature. Alternatively, or in addition, articular surface regions 68may have distinct diameters, as measured between opposite borders ofeach surface region, and/or distinct perimeter shapes (e.g., circularand oval, among others).

Set 134 may be composed of fixed articular members 76 (interchangeablytermed side articular members or body members (e.g., cup members)) withdifferent side articular surface regions 72. The fixed articular membersand/or surface regions 72 may have different outer diameters relative toone another, as shown. Alternatively, or in addition, the fixedarticular members may have distinct shapes (e.g., circular and oval,among others), different heights, or the like. Recess 98 may (or maynot) have the same size and shape in each fixed articular member.

Set 136 may be composed of stem components and/or stem portions 56having different shafts 60. For example, the shafts may differ indiameter (as shown), length, cross-sectional shape, or any combinationthereof, among others. Collar portion 80, if present, also oralternatively may differ among members of set 136, for example,differing in diameter or height, among others.

An operative prosthesis 50 (e.g., see FIGS. 1, 2, and 6) may beassembled from any suitable combination of a dish member 54 from set132, a cup member 76 from set 134, and a stem component 84 or stemportion 56 from set 136. A component from each set may be selected thatgives a preferred fit (e.g., the best expected fit or measured fit) fora recipient of the prosthesis. Selection of each component may beperformed before or during a surgical procedure on the recipient.

A prosthesis with a compound head having a side articular member and anend/top articular member may offer substantial advantages. For example,the compound head may provide substantial advantages over a one-pieceprosthetic head, such as offering a surgeon the ability to independentlyselect the size/shape of the top and side articular surface regions ofthe prosthesis. As a result, the articular surface regions of theinstalled prosthesis may better approximate the natural (removed) radialhead and may complement articular surfaces of adjacent bones moreaccurately, thereby improving joint function and reducing wear. Also,the top/end articular surface region of the prosthesis may float duringuse. For example, the top/end articular surface region may bedynamically centered on the capitellum and/or dynamically angled withrespect to the long axis of the stem portion of the prosthesis duringmovement of the radial bone at the elbow joint.

Further aspects of radial head prostheses having a floating articularmember are described elsewhere in the present disclosure (e.g., seeSection III). In some cases, the prosthesis may have a single floatingarticular member for contact with both the ulna and the humerus (seeExamples 3 and 9). The articular member may provide a pair of articularsurface regions for respective engagement with the ulna and the humerus,with the pair of articular surface regions being fixed relative to oneanother (e.g., with both surface regions being formed by the samecontinuous surface of the articular member). In some cases, the pair ofarticular surface regions may be movable relative to one another (e.g.,slidable transversely and/or rotatable (e.g., tiltable)).

II. Prosthesis Installation

This section describes exemplary methods of installing a radial headprosthesis having any suitable combination of the features, aspects, andcomponents of the present disclosure. The methods also or alternativelymay be described as methods of repairing an elbow joint. In any event,the method steps of this section and elsewhere in the present disclosuremay be performed in any suitable order and in any suitable combination.

An elbow joint and/or radial bone may be selected. The elbow jointand/or radial bone may have a damaged (e.g., injured) or missing radialhead.

The radial bone may be prepared to receive a radial head prosthesis. Thenatural radial head may be removed, if present. For example, the radialbone may be cut to remove the radial head. A medullary cavity of theradial bone may be prepared to receive the stem portion of a prosthesis.For example, the cavity may be reamed and/or broached, among others. Thecavity may be sized according to the diameter and/or length of a stemportion to be received in the cavity.

A prosthesis for installation may be selected. Selection of theprosthesis may include selecting suitable stem and head components ofthe prosthesis based on one or more characteristics of the particularelbow joint and/or radial bone to be repaired. For example, a stemcomponent or stem portion may be selected according to the size of themedullary cavity or radial bone, the length of radial bone removed, orthe like. Alternatively, or in addition, a side articular member of thehead portion, or the entire head portion, may be selected based on themedial-lateral offset of the capitellum relative to the radial notch inthe recipient. Furthermore, a floating articular member or dish membermay be selected based on a characteristic of the capitellum in therecipient, such as the size, shape, and/or position of the capitellum.Selection of each component may be based on at least one measurement ofthe elbow joint and/or radius. The measurement may result from ameasuring device, such as calipers, a radiographic scale, temporaryinstallation of a trial prosthesis or trial component thereof, or thelike. In some cases, aspects of the radial prosthesis may be selectedbased on one or more characteristics of another prosthesis (e.g., anulnar prosthesis and/or a humeral prosthesis) to be contacted by theradial prosthesis.

The stem portion of the prosthesis may be inserted into the medullarycavity of the radial bone. The stem portion may be fixed to the radiuswith the stem portion in the medullary cavity. Fixing the stem portionmay be achieved by the act of insertion or may be effected or augmentedafter insertion of the stem portion (e.g., with fasteners).

The head portion of the prosthesis may be placed in operative attachment(interchangeably termed operative connection) to the stem portion. Thehead portion, or one or more articular members thereof, may beoperatively connected to the stem portion before or after the stemportion is inserted into the medullary cavity.

The head portion of the prosthesis may be assembled. For example, a toparticular member of the prosthesis may be operatively connected to aside articular member. This assembly may be performed before or afterthe side articular member and/or the head portion is operativelyconnected to the stem portion.

Assembly of the prosthesis may be performed during manufacture orintraoperatively. In some cases, intraoperative assembly may bepreferable, to permit a surgeon to select suitable components in theoperating room according to the specific anatomy of the recipient. Insome embodiments, intraoperative assembly may include connection of aretainer, to establish a predefined range of motion for a head memberand/or articular member.

III. Examples

The following examples describe selected aspects and embodiments of thepresent disclosure including exemplary radial head prostheses(interchangeably termed implants) and methods of installing theprostheses. The components, aspects, and features of the implantsdescribed in each of these examples may be combined with one another andwith the implants described above, in any suitable combination. Theseexamples are intended for illustration and should not limit the entirescope of the present disclosure.

Example 1 Prosthesis with a Biased Dish Member

This example describes exemplary prostheses having a floating articularmember with a position biased, along and/or about at least one axis, byat least one biasing member (e.g., at least one elastic member, such asa spring); see FIGS. 14 and 15.

FIG. 14 shows another embodiment 150 of a prosthesis having a floatingdish member 54 for engagement with the capitellum. Prosthesis 150 may bestructured generally as described above for prosthesis 50 (see SectionI), except that dish member 54 has additional degrees of freedom and hasa biased position with respect to cup member 76 and/or along long axis122.

A modified retainer 152 may determine the range of motion and the biasedposition of dish member 54 (compare with retainer 96; see FIGS. 4-6, 9,10A, and 10B). Each retainer component 154 of retainer 152 may define anopening 156, which is larger than the opening of retainer 96. Opening156 provides clearance for vertical movement of dish member 54, asindicated by a double-headed arrow at 158, along long axis 122 (and/oralong the head axis; see FIG. 6). Accordingly, dish member 54 can movetranslationally parallel to long axis 122. Also, the retainer providessufficient clearance for the dish member to rotate about a fixed orvariable axis transverse to long axis 122, as indicated by adouble-headed rotation arrow at 160, to change the orientation (thetilt) of the dish member. The ability of dish member 54 to tilt withrespect to the stem portion may allow dish member 54 to achieve a closerstatic and/or dynamic fit to the capitellum. The dish member and/or thehead portion, here and elsewhere in the present disclosure, may becapable of rotating (tilting) any suitable angle from a neutral (e.g.,untilted) position, such as at least about 3, 5, 7, 10, or 20 degrees,and/or less than about 40, 30, 20, 15, or 10 degrees, among others.

Retainer 152 also may provide at least one biasing member 162, whichhere and elsewhere in the present disclosure may be flexible, and may bedescribed as a resilient member, an elastic member, and/or a springmember. Biasing member 162 may bias the position of dish member 54, suchas along axis 122. For example, the biasing member may urge the dishmember upward, away from the stem portion of the prosthesis, and towardsthe capitellum. The biasing member may function as a shock absorberand/or may encourage a more constant and uniform engagement of thecapitellum as the radius travels through its range of motion withrespect to the other bones of the elbow joint. Here, the biasing memberis structured as a leaf spring. In other cases, the biasing member maybe a coil spring, a resilient pad, a fluid-filled bladder, or the like.However, any suitable biasing mechanism may be incorporated into thehead portion of the prosthesis to resiliently position dish member 54(and/or the head portion) along and/or about any suitable axis or axes.The biasing mechanism may store mechanical energy and supply a restoringforce that urges dish member 54 (and/or the head portion) toward anequilibrium or resting position.

FIG. 15 shows another embodiment 170 of a prosthesis having a floatingdish member 54 for engagement with the capitellum. Prosthesis 170 may bestructured generally as described above for prosthesis 150 (see FIG.14), with dish member 54 being capable of axial (e.g., vertical) motionand transverse (e.g., horizontal) motion, and having a biased positionwith respect to cup member 76 and/or along the long axis of theprosthesis. Prosthesis 170 has a retainer 172 containing a biasingmember 174 (e.g., a leaf spring) that is a discrete component relativeto the retainer and dish member 54. Biasing member 174 may be disposedbetween surface regions of dish member 54 and retainer 172, with thebiasing member inside (as shown here) or outside the opening(s) definedby the retainer. In some embodiments, the biasing member may be integralto dish member 54 (e.g., formed by a resilient base region of the dishmember). In some embodiments, the biasing member may be disposed underthe retainer, namely, between the retainer and the floor of cup member76. With this arrangement, the retainer may be capable of moving axially(e.g., vertically) within the cup member, through a predefined range ofvertical motion.

Example 2 Prosthesis with Resilient Retainer

This example describes an exemplary prosthesis 190 having a resilientretainer 192 that captures a floating dish member 54 in a cup member 76;see FIG. 16.

Prosthesis 190 may be structured generally as described above forprostheses 50, 150, and 170 (see Section I and Example 1). For example,dish member 54 may be capable of sliding transversely in cup member 76,indicated at 120, to dynamically center the dish member on thecapitellum. However, the dish member may have a curved and convex (e.g.,spherical) bottom surface region 194 that allows the dish member torotate (e.g., by rocking), indicated by a double-headed arrow at 160,about a fixed or variable transverse axis, to a tilted configurationthat changes the angle defined between the dish member and the long axisof stem portion 56.

Dish member 54 may be held in cup member 76 by retainer 192 thatfunctions generally like retainer 96 (see FIG. 4), except that retainer192 provides more clearance for vertical movement of the dish member andis least partially elastic. For example, retainer 192 may have anelastic ring portion 196 sandwiched between and affixed to retainermembers 198, 200 that are less elastic. The elastic region of retainer192 may provide a biasing mechanism that biases the position of dishmember 54 along a vertical axis, biases the rotational (tilted) positionof the dish member, and/or that acts as an elastic bumper that can becontacted by a base region 106 of the dish member to cushion and/orlimit lateral motion 120 of the dish member.

Example 3 Prosthesis with Shock Absorption

This example describes an exemplary prosthesis 210 having a resilient,shock-absorbing member 212 disposed within a head portion 52; see FIG.17.

The head portion may include a single articular member 214 (whichinterchangeably may be described as a head member or an inverted cupmember) that forms top articular surface region 68 and side articularsurface region 72 for respective articulation with the humerus and theulna. Head member 214 may be configured to float with respect to a stemcomponent 84 that provides stem portion 56 and shoulder 80. Moreparticularly, head member 214 and/or head portion 52, as a unit, may becapable of transverse motion 120 and rotational motion 160, with respectto stem portion 56.

Head member 214 may house a retainer assembly 216 that is held withinthe head member by at least one detent 218. The retainer assembly mayinclude shock-absorbing member 212, which may be structured as an O-ringsandwiched between upper and lower members 220, 222 of retainer assembly216. Upper and lower members 220, 222 may be spaced from one another, asshown, to permit deformation of shock-absorbing member 212. Theshock-absorbing member may deform in response to a vertical load on thehead portion (parallel to the long axis of the stem portion), a momentapplied to the head portion (e.g., urging the head to tilt), or thelike.

Retainer assembly 216 may define a cavity 224 sized and shaped toreceive and trap a top protrusion 226 of stem component 84. The topprotrusion may have a convex and curved (e.g., spherical) surface region228 that contacts the ceiling of cavity 224 to facilitate rotationalmotion 160 (e.g., with surface region 228 rolling along the ceiling ofthe cavity).

Stem portion 56 may have a rough surface 230, such as titanium plasmacoat, to facilitate bony ongrowth that anchors the stem portion morestably in the radial bone.

Example 4 Prostheses with Distinct Joints for Transverse and RotationalMotion

This example describes exemplary prostheses each having a first jointthat permits transverse motion 120 of an articular member and a secondjoint that permits rotational motion 160 of the articular member; seeFIGS. 18A, 18B, and 19.

FIGS. 18A and 18B show prostheses 250 and 250 a that each permit dishmember 54 to undergo transverse motion 120 and pivotal motion 160 viadistinct joints. Dish member 54 is capable of transverse motion 120, inthis case, translational motion, via sliding at a planar joint 252, asdescribed above (e.g., see Section I). Dish member 54 also is capable ofrotational motion, in this case pivotal motion, via a spherical joint254. Joint 254 may be formed by a ball member 256 defined by stemcomponent 84 and a polymer-lined socket 258 defined by a protruding baseregion 260 of cup member 76, or vice versa, among others. Pivotal motionat joint 254 allows the entire head portion (including cup member 76 anddish member 54) to be rotated (e.g., tilted) relative to the stemportion.

Prostheses 250 and 250 a may have different resilient members.Prosthesis 250 (FIG. 18A) may have one or more resilient sheets 262(e.g., pads or annular sheets) disposed between facing surface regions264, 266 of the head portion/cup member 52/76 and stem component 84,respectively. The sheet(s) may cushion contact between the head portionand the stem component when the head portion is tilted close to itsrotational limit. Prosthesis 250 a (FIG. 18B) may have a resilient ring268 disposed between head portion 52 and stem component 84. Ring 268 may(or may not) be in contact with surface regions 264, 266 of both thehead portion and the stem component when the head portion is in aneutral position (as shown) and may deform as the head portion is tiltedwith respect to the stem portion, to cushion tilting motion and/or tobias the rotational position of the head portion, among others.

FIG. 19 shows a radial head prosthesis 280 having a floating articularmember 282 for articulation with the capitellum. Floating articularmember 282 defines a concave surface region 68 for contacting thecapitellum. Articular member 282 may be movable with respect to a fixedarticular member 76 (a cup member) that provides an outer side wall 72for articulation with the ulna. Articular member 76 may be fixed withrespect to stem portion 56, and may be formed as one piece with the stemportion, as shown here, or may be fixedly connectable to the stemportion by attaching discrete components to each other (e.g., seeSection I).

Floating articular member 282 may be one piece or two or more pieces.For example, in the depicted embodiment, articular member 282 iscomposed of an upper element 284, which may be formed of metal, and alower element 286, which may be formed of polymer. Elements 284 and 286may be fixed to one another such that the elements move together as aunit. Upper element 284 contacts the capitellum, and the lower element286 supports the upper element.

Articular member 282 may be pivotably connected to and supported by asupport member 288 (interchangeably termed a post member), which may beformed of metal. Articular member 282 and support member 288collectively may form a pivotable joint 290 that permits rotationalmotion 160 of articular member 282 with respect to stationary regions ofthe prosthesis (e.g., cup member 76 and stem portion 56). The pivotablejoint may, for example, be a ball-and-socket joint. In the depictedembodiment, lower element 286 of articular member 282 defines a socket292 and support member 288 defines a ball member 294 that is receivedand trapped in the socket. In other embodiments, the positions of thesocket and ball member may be reversed.

Support member 288 may be held in cup member 76 by a retainer 96 engagedwith a detent 102 formed by the cup member. Retainer 96 may define anaperture 296 sized to receive a portion of the support member. Moreparticularly, support member 288 may have a base 298 and a neck region300 projecting upward from the base to ball member 294. The neck regionmay be sized to extend through aperture 296, with the diameter of theaperture substantially greater than that of the neck region.Accordingly, the neck region can travel laterally in aperture 296, whichproduces transverse motion 120 of floating articular member 282 withrespect to the fixed portions of the prosthesis. Base 298 may be toowide to fit through aperture 296, which traps support member 288 in cupmember 76. Base 298 may slide transversely (in this case,translationally) on a floor 302 of the cup member to form a movableplanar joint 304. Floor 302 may be formed by a polymer insert or liner306 disposed at the bottom of a recess defined by a metal portion of thecup member.

Example 5 Prosthesis with a Dish Member that Slides and Rocks

This example describes exemplary prostheses having a slidable dishmember that is capable of sliding and/or rocking motion on various cupmember surface regions; see FIGS. 20-22.

FIG. 20 shows a radial head prosthesis 320 having a slidable dish member322 for engagement with the capitellum. Prosthesis 320 has a cup member76 defining a recess 324 having a concave floor region 326. The floorregion may be curved in a concave manner (e.g., spherical), and may becoaxial with articular surface region 72 of the cup member and/or thearticular surface of the capitellum, when the dish member is in use.Floor region 326 may be slidably engaged with a convex underside 328 ofdish member 322. Underside 328 may be spherical, with a smaller radiusthan floor region 326 of the cup member. Accordingly, dish member 322can undergo transverse motion 120 along a curved path defined by floorregion 326 and can undergo rotational motion 160 by rocking/rolling fromside to side on floor region 326. Dish member 322 may (or may not) betrapped in cup member 76 with a retainer. In other embodiments, floorregion 326 may be planar, and underside 328 still may be convex, such asspherical.

FIG. 21 shows a radial head prosthesis 340 having a slidable dish member342 for engagement with the capitellum. The dish member has a flatbottom surface region 344 that is slidably engaged with a flat floorregion 346 of a cup member 76. Dish member 342 can undergo transversemotion 120 at a planar joint 348. The dish member may or may not betrapped in cup member 76.

FIG. 22 shows another radial head prosthesis 360 having a slidable dishmember 362 for engagement with the capitellum. The dish member has aspherical concave bottom surface region 364 that is slidably engagedwith a complementary, spherical floor region 366 of a cup member 76, topermit transverse motion 120. Dish member 362 can slide along curvedfloor region 366, which may have the same radius as concave surfaceregion 364 of the dish member. In other embodiments, floor region 364may be provided by a retainer that attaches the dish member to the cupmember.

Example 6 Prosthesis with a Dish Member Received Transversely

This example describes an exemplary prosthesis 380 having a floatingdish member 54 received transversely during assembly of the prosthesis;see FIG. 23.

Prosthesis 380 has a head portion 52 composed of dish member 54 forarticulation with the capitellum, a body or housing member 382, and adoor or cap member 384. Body member 382 is analogous to cup member 76 ofprosthesis 50 (e.g., see FIGS. 4 and 7). The body member may beconfigured to engage a stem component 84 of the prosthesis, to fix thebody member to the stem component. Body member 382 may have a sidearticular surface region 72 for articulation with the radial notch ofthe ulna.

Body member 382 may define a cavity 386 sized to receive a base region106 of the dish member. Cavity 386 may provide an entryway or mouth 388on a side region of body member 382, which allows dish member 54 to beplaced transversely into the cavity. Door member 384 may be attachableto body member 382, to close the lateral entryway to cavity 386, therebytrapping the base of the dish member in the cavity. Door member 384 maybe attached to body member 382 by any suitable fastening mechanism, suchas a pair of clips 390 that engage body member 382.

In the depicted embodiment, the upper region of dish member 54 isdisposed above body member 382, after the prosthesis is assembled. Inother embodiments, body member 382 may be structured as a cup membercapable of receiving a majority of the upper region of dish member 54.For example, in the assembled prosthesis, dish member 54 may not projectsubstantially (or at all) above the top of body member 382.

Example 7 Prosthesis with a Dish Member Retained by a Clip

This example describes an exemplary prosthesis 400 having a slidabledish member 402 held in a cup member 76 by a clip 404; see FIGS. 24 and25.

Clip 404 may be generally C-shaped (e.g., a split ring) with a gap 406that permits the clip to be placed around dish member 402. The gap alsoallows the clip to be compressed to a smaller diameter, for placement ofthe clip into the cup member, below an overhanging lip or flange 408thereof. Clip 404 then can expand resiliently back to a larger diameter,to trap dish member 402 in cup member 76. Clip 404 may be received in acircumferential groove 410 defined by a side wall of dish member 402.Groove 410 may be deep enough to receive a greater portion of clip 404when the clip is compressed. Clip 404 may have a bevel 412 thatfunctions to urge the clip radially inward, deeper into groove 410, whenthe dish member is being urged downward into the cup member duringassembly of the head portion. Cup member 76 may have a polymer liner 414to facilitate sliding of dish member 402 against the cup member and/orto reduce swarf, among others.

Example 8 Prosthesis with a Dish Member Retained by a Pin

This example describes an exemplary prosthesis 420 having a floatingdish member 422 held in a cup member 76 by a pin 424; see FIGS. 26 and27.

Pin 424 may be placed through an opening defined by a side wall regionof cup member 76 and into a slot 426 defined by dish member 422. Therelative size, geometry, and position of the pin and slot may determinethe permitted range of motion for dish member 422. For example, the dishmember may be permitted to undergo transverse motion 120 by sliding,and, optionally, rotational motion 160 by rocking. The dish member(and/or a floor region 428 of cup member 76) may have a curved (e.g.,spherical) surface region 430 that facilitates rotation by rocking (arolling motion). Cup member 76 may (or may not) have a polymer liner432.

Example 9 Prostheses with a Floating Head Member

This example describes exemplary prostheses having a floating headmember 214 that articulates with both the humerus and the ulna; seeFIGS. 28-31.

FIG. 28 shows a radial head prosthesis 440 having a stem assembly 442that is connectable a head portion 52 of the prosthesis. Stem assembly442 may include a base 444 that provides stem portion 56 and a mountingmember 446 that mates with the base. The mounting member may define asupport member 448 disposed above stem portion 56 and sized to bemovably trapped in head portion 52.

Head portion 52 may include head member 214 and a pair of polymer liners450 and 452. Head member 214 provides articular surface regions 68 and72, and may be described as a dish member and/or an inverted cup member.The head member may be attached to polymer liners 450, each of which maybe snap-locked in place.

Head portion 52 may be slidably connected to mounting member 446 of stemassembly 442. A support member 448 of the mounting member may bereceived and trapped in a cavity defined collectively by the headportion and a shoulder region 454 of base 444 of the stem assembly. Therelative sizes of support member 448 and the cavity may determine therange of permitted motion for head portion 52 and/or head member 214.

Head member 214, mounting member 446, and liners 450 and 452 may bepre-assembled to form a head assembly including head portion 52, with ashaft 456 of mounting member 446 projecting from the underside of thehead portion. The head assembly may be attached to base 444, such as bymating, to form the complete prosthesis.

Head portion 52 and/or head member 214 may float with respect to thestem portion. More particularly, the head portion/member may be free toundergo transverse motion 120 and rotational motion 160 at a same joint458. For example, the head portion may rock on a curved (e.g.,spherical) surface region 460 of support member 448, to change the tiltof the head portion with respect to the stem portion.

FIG. 29 shows another radial head prosthesis 480 having a stem component482 that is operatively connectable to a floating head portion 52 of theprosthesis. The stem component may be structured generally like stemassembly 442 (see FIG. 28) except that the stem component may be onlyone piece. A support member 448 of the stem component may be trapped inhead portion 52. During assembly, a resilient liner 484 may be placedonto support member 448, and then the liner and support member placedinto a cavity 486 defined by head member 214. The head member may haveat least one detent 488 to prevent removal of liner 484 from cavity 486.Head portion 52 and/or head member 214 may be free to undergo transversemotion 120 and rotational motion 160 in the assembled prosthesis, asdescribed above for prosthesis 440 (see FIG. 28).

FIG. 30 shows yet another radial head prosthesis 500 having a stemcomponent 502 that is operatively connectable to a floating head portion52 (head member 214) of the prosthesis. Stem component 502 may include abase member 504 that forms stem portion 56, and a polymer cap 506attached to an upper region of the base member. An enlarged top portionof stem component 502 may be received in a cavity 486 defined by headmember 214. A retainer 508, such as a clip (e.g., a split ring), may beinstalled to capture the top portion of the stem component in headmember 214. Retainer 508 may be received in a circumferential recess 510defined inside head member 214. Retainer 508 may have an inclinedsurface region 512 that causes the retainer to be expanded radiallyoutward, deeper into recess 510, as the top portion of the stemcomponent is being forced into head member 214, past retainer 508.

FIG. 31 shows yet another radial head prosthesis 520 having a stemcomponent 522 that is operatively connectable to a floating head portion52 of the prosthesis. Stem component may include a base member 524 thatprovides stem portion 56, and a mounting member 526 that providessupport member 448. The support member may be trapped in the headportion by a retainer 528.

Example 10 Selected Embodiments 1

This example describes selected embodiments of a radial head prosthesiswith a slidable head portion and/or a slidable articular member of thehead portion, and methods of using the prosthesis. The selectedembodiments are presented as a series of numbered paragraphs.

1. A method of repairing an elbow joint, the method comprising: (A)selecting a prosthesis including a head portion operatively connected oroperatively connectable to a stem portion such that the head portion,and/or an articular member thereof, is slidable transversely to a longaxis defined by the stem portion; and (B) installing the prosthesis suchthat the prosthesis is mounted to a radial bone and the head portionarticulates with an ulnar bone and a humeral bone.

2. The method of paragraph 1, wherein the step of installing includes astep of disposing the stem portion in the radial bone.

3. The method of paragraph 1 or 2, further comprising a step ofoperatively connecting the head portion and/or the articular member tothe stem portion during a surgical procedure.

4. The method of paragraph 3, wherein the step of operatively connectingis performed after the stem portion is disposed in the radial bone.

5. The method of paragraph 1, wherein the head portion includes a firstarticular member that articulates with the ulnar bone and a secondarticular member that articulates with the humeral bone, and wherein thefirst and second articular members are discrete and movable relative toone another with the head portion operatively connected to the stemportion.

6. The method of paragraph 5, wherein, with the head portion operativelyconnected to the stem portion, the first articular member is fixed withrespect to the stem portion and the second articular member is movablewith respect to the stem portion.

7. The method of paragraph 5 or 6, wherein the first articular memberincludes a cup member.

8. The method of paragraph 7, wherein the second articular member isdisposed in the cup member.

9. The method of any of paragraphs 1 to 8, wherein the head portionand/or the articular member is slidable along a linear path with respectto the stem portion.

10. The method of any of paragraphs 1 to 9, wherein the head portionand/or the articular member is slidable along a curved path with respectto the stem portion.

11. The method of paragraph 10, wherein curved path is defined by atleast one spherical surface region.

12. The method of any of paragraphs 1 to 11, wherein head portionincludes a top articular surface region to contact the capitellum and aside articular surface region to contact the radial notch, and whereinthe top articular surface region is movable with respect to the sidearticular surface region.

13. The method of paragraph 12, wherein the side articular surfaceregion is fixed with respect to the stem portion, and wherein the toparticular surface region is movable transversely with respect to thestem portion.

14. The method of paragraph 12 or 13, wherein the top articular surfaceregion is spherical.

15. The method of any of paragraphs 12 to 14, wherein the top articularsurface region is provided by an articular member that is spring-biased.

16. The method of paragraph 15, wherein the stem portion defines a longaxis, and wherein the articular member is spring-biased along an axisthat is at least generally parallel to the long axis.

17. The method of any of paragraphs 12 to 16, wherein the prosthesis isinstalled in a recipient, wherein the top articular surface region has aradius of curvature and is provided by first articular member, whereinthe side articular surface region is provided by a second articularmember, further comprising a step of selecting the first articularmember from a set of two or more first articular members havingdifferent radii of curvature, and a step of operatively connecting theselected first articular member to the second articular member.

18. The method of paragraph 17, wherein the second articular member hasa diameter, further comprising a step of selecting the second articularmember from a set or two or more second articular members havingdifferent diameters.

19. A method of repairing an elbow joint, the method comprising: (A)selecting a prosthesis including a head portion having a first articularmember and a second articular member that are discrete from one another,the head portion being operatively connected or operatively connectableto a stem portion with the first and second articular members aremovable relative to one another in the absence of bone; and (B)installing the prosthesis such that the prosthesis is mounted to aradial bone, the first articular member articulates with an ulnar bone,and the second articular member articulates with a humeral bone.

20. The method of paragraph 19, wherein the first articular member isfixed with respect to the stem portion when the head portion isoperatively connected to the stem portion.

21. The method of paragraph 19 or 20, wherein the first articular memberincludes a cup member, and wherein the second articular member includesa dish member.

22. The method of paragraph 21, wherein the dish member is disposed inthe cup member when the head portion is operatively connected to thestem portion.

23. The method of paragraph 21 or 22, wherein the dish member isslidable transversely to a long axis defined by the stem portion whenthe head portion is operatively connected to the stem portion.

24. The method of any of paragraphs 21 to 23, wherein the secondarticular member has a spring-biased position with respect to the firstarticular member.

25. The method of paragraph 24, wherein the position of the secondarticular member is spring-biased along an axis that is at leastgenerally parallel to a long axis defined by the stem portion.

26. The method of any of paragraphs 19 to 25, wherein the secondarticular member is pivotable with respect to the first articularmember.

27. The method of any of paragraphs 19 to 26, wherein the secondarticular member is connected to the first articular member by aretainer received in a cup region of the first articular member.

28. The method of paragraph 27, further comprising a step ofsnap-fitting the retainer in the cup region such that the retainer isprevented from removal.

29. The method of paragraph 27 or 28, wherein retainer includes at leasttwo discrete pieces that each receives a portion of the second articularmember.

30. The method of paragraph 27, wherein the retainer includes a fastenerthat extends from an opening defined by the first articular member intoan opening defined by the second articular member.

31. A prosthesis for elbow repair, comprising: (A) a stem portionconfigured to be received in a radial bone; and (B) a head portionincluding a first articular region configured to articulate with anulnar bone and a second articular region configured to articulate with ahumeral bone, the head portion being operatively connected oroperatively connectable to the stem portion such that the firstarticular region, the second articular region, or both the first andsecond articular regions are slidable transversely to a long axisdefined by the stem portion.

32. A prosthesis for elbow repair, comprising: (A) a stem portionconfigured to be received in a radial bone; and (B) a head portionincluding a first articular region configured to articulate with anulnar bone and a second articular region configured to articulate with ahumeral bone, the head portion being operatively connected oroperatively connectable to the stem portion such that the firstarticular region is fixed with respect to the stem portion and thesecond articular region is slidable transversely to a long axis definedby the stem portion.

33. The prosthesis of paragraph 32, wherein the second articular regionhas a spring-biased position with respect to the first articular region.

34. A system for elbow repair, comprising: (A) a stem portion; (B) afirst articular member operatively connected or connectable to the stemportion and configured to articulate with a radial notch of an ulnarbone; and (C) a second articular member configured to be slidablyconnected to the first articular member and to articulate with acapitellum of a humeral bone.

35. The system of paragraph 34, further comprising a set of firstarticular members that includes the first articular member, each firstarticular member being operatively connected or connectable to a stemportion and each having a different diameter.

36. The system of paragraph 35, wherein each first articular member isoperatively connectable to a same stem portion.

37. The system of paragraph 35, wherein each first articular member isincluded in a distinct pre-formed component that includes a stemportion.

38. The system of any of paragraphs 34 to 37, further comprising a setof second articular members that includes the second articular member,each second articular member being slidably connectable to the firstarticular member and each having an articular surface region with adifferent curvature.

39. The system of any of paragraphs 34 to 38, further comprising aretainer to slidably connect the second articular member to the firstarticular member.

40. The system of paragraph 39, wherein the first and second articularmembers are formed of metal and the retainer is formed of plastic.

41. The system of any of paragraphs 34 to 40, wherein the secondarticular member has a spring-biased position with respect to the firstarticular member when the second articular member is slidably connectedto the first articular member.

Example 11 Selected Embodiments II

This example describes additional selected embodiments of a prosthesiswith a slidable head portion and/or a slidable articular member of thehead portion, and methods of using the prosthesis. The selectedembodiments are presented as a series of numbered paragraphs.

A1. A method of replacing an end of a radial bone with a prosthesishaving a fixed member and a floating member, the method comprising:installing the prosthesis such that the prosthesis is attached to aradial bone, the fixed member articulates with an ulnar bone, and thefloating member articulates with a humeral bone.

A2. The method of paragraph A1, wherein at least one of the ulnar boneand the humeral bone includes a prosthetic region, and wherein at leastone of the fixed member and the floating member articulates at least inpart with a prosthetic region.

A3. The method of paragraph A1 or A2, wherein the fixed member includesa cup portion, and wherein a majority by volume of the floating memberis disposed in the cup portion after the step of installing.

A4. The method of any of paragraphs A1 to A3, wherein the prosthesisincludes a stem portion defining a long axis, and wherein the floatingmember is capable of moving as a unit transversely to the long axisduring movement of the radial bone with respect to the ulnar bone and/orhumeral bone after the step of installing.

A5. The method of any of paragraphs A1 to A4, wherein the floatingmember is capable of moving translationally during movement of theradial bone with respect to the ulnar bone and/or humeral bone after thestep of installing.

A6. The method of any of paragraphs A1 to A5, wherein the floatingmember is rotatable with respect to the fixed member during movement ofthe radial bone with respect to the ulnar bone and/or humeral bone afterthe step of installing.

A7. The method of any of paragraphs A1 to A6, wherein the prosthesisincludes a head portion that includes the fixed member and the floatingmember, and wherein the head portion includes at least one resilientmember that is deformable to bias a position of the floating member withrespect to the fixed member.

A8. A method of replacing a proximal end of a radial bone with aprosthesis having a stem portion and a head portion, the methodcomprising: installing the prosthesis in an operative configuration,with the stem portion mounted to a radial bone, a first member of thehead portion articulating with an ulnar bone, a second member of thehead portion articulating with a humeral bone, and the second membermovably connected to the first member.

A9. The method of paragraph A8, wherein the stem portion defines a longaxis, and wherein the first member and the second member are movablerelative to each other in a direction transverse to the long axis duringmovement of the radial bone with respect to the ulnar bone and/orhumeral bone after the step of installing.

A10. The method of paragraph A8 or A9, wherein the second member ismovable translationally with respect to the first member in theoperative configuration.

A11. The method of any of paragraphs A8 to A10, wherein the secondmember is rotatable with respect to the first member in the operativeconfiguration.

A12. The method of any of paragraphs A8 to A11, wherein at least one ofthe ulnar bone and the humeral bone includes a prosthetic region, andwherein at least one of the first member and the second memberarticulates at least in part with a prosthetic region.

A13. The method of any of paragraph A8 to A12, wherein the second memberis connected to the first member by a movable joint that permitstranslational motion and rotational motion of the first and secondmembers relative to each other.

A14. The method of any of paragraphs A8 to A12, wherein the secondmember is connected to the stem portion by a slidable joint and apivotable joint that are distinct from each other.

A15. A method of replacing a proximal end of a radial bone, the methodcomprising: installing a prosthesis, with a stem portion thereof mountedto a radial bone and an articular member of the prosthesis articulatingwith a humeral bone and operatively connected to the stem portion suchthat the articular member is permitted to float as a unit transverselyto a long axis defined by the stem portion.

A16. The method of paragraph A15, wherein the step of installingdisposes the articular member for articulation with an ulnar bone.

A17. The method of paragraph A15 or A16, wherein the articular memberincludes an inverted cup member that forms a first surface region forarticulation with the humeral bone and a second surface region forarticulation with the ulnar bone.

A18. The method of any of paragraphs A15 to A17, wherein step ofinstalling permits the articular member to rotate as a unit with respectto the stem portion to change a tilt of the articular member withrespect to the stem portion.

A19. The method of any of paragraphs A15 to A18, wherein the articularmember is capable of moving translationally with respect to the stemportion while remaining operatively connected to the stem portion.

A20. The method of any of paragraphs A15 to A19, wherein the articularmember is operatively connected to the stem portion by a movable jointincluding a spherical surface region corresponding to no more thanone-half of a complete sphere.

B1. A device for replacing a proximal end of a radial bone, comprising:(i) a stem portion that mounts to a radial bone; and (ii) a head portionoperatively connected or connectable to the stem portion and including afixed member to articulate with an ulnar bone and a floating member toarticulate with a humeral bone.

B2. The device of paragraph B1, wherein the fixed member includes a cupportion, and wherein a majority by volume of the floating member isdisposed in the cup portion when the head portion is operativelyconnected to the stem portion.

B3. The device of paragraph B1 or B2, wherein the floating memberdefines a concave articular surface region on a top side of the headportion.

B4. The device of any of paragraphs B1 to B3, wherein the floatingmember is movable translationally while the head portion remainsoperatively connected to the stem portion and the stem portion remainsstationary.

B5. The device of paragraph B4, wherein the floating member is movablein a plane that is transverse to a long axis defined by the stem portionwhile the head portion remains operatively connected to the stem portionand the stem portion remains stationary.

B6. The device of any of paragraphs B1 to B5, wherein the floatingmember is rotatable while the head portion remains operatively connectedto the stem portion and the stem portion remains stationary.

B7. The device of any of paragraphs B1 to B6, wherein, when the headportion is operatively connected to the stem portion, the floatingmember is operatively connected to the fixed member to form a joint thatpermits translational motion and rotational motion of the floatingmember relative to the fixed member.

B8. The device of any of paragraphs B1 to B6, wherein the floatingmember is operatively connected to the stem portion by a first jointthat permits transverse motion of the floating member with respect tothe stem portion and by a second joint that permits pivotal motion ofthe floating member with respect to the stem portion.

B9. The device of any of paragraphs B1 to B8, wherein the head portionincludes a resilient member that biases a position of the floatingmember relative to the fixed member.

B10. The device of any of paragraphs B1 to B9, wherein at least one ofthe fixed member and the floating member is configured to articulate atleast in part with a prosthetic region of an ulnar bone or a humeralbone.

B11. A device for replacing a proximal end of a radial bone, comprising:(i) a stem portion that mounts to a radial bone; and (ii) a head portionoperatively connected or connectable to the stem portion and including afirst member to articulate with an ulnar bone and a second member toarticulate with a humeral bone, the second member being movablyconnected to the first member when the head portion is operativelyconnected to the stem portion.

B12. The device of paragraph B11, wherein the second member is movabletranslationally with respect to the first member while the head portionremains operatively connected to the stem portion.

B13. The device of paragraph B11 or B12, wherein the second member ismovable rotationally with respect to the first member while the headportion remains operatively connected to the stem portion.

B14. A device for replacing a proximal end of a radial bone, comprising:(i) a stem portion that mounts to a radial bone; and (ii) a head portionincluding an articular member for articulation with a humeral bone, thehead portion being operatively connected or connectable to the stemportion such that the articular member is permitted to float as a unitrelative to the stem portion and transversely to a long axis defined bythe stem portion.

B15. The device of paragraph B14, wherein the articular member isconfigured to articulate with an ulnar bone.

C1. A method of replacing an end of a bone with a prosthesis having afixed member and a floating member, the method comprising: installingthe prosthesis such that the prosthesis is attached to a first bone, thefixed member articulates with a second bone, and the floating memberarticulates with a third bone.

C2. The method of paragraph C1, wherein at least one of the second andthird bones includes a prosthetic region, and wherein at least one ofthe fixed member and the floating member articulates at least in partwith a prosthetic region.

C3. The method of paragraph C1 or C2, wherein the fixed member includesa cup portion, and wherein a majority by volume of the floating memberis disposed in the cup portion after the step of installing.

C4. The method of any of paragraphs C1 to C3, wherein the prosthesisincludes a stem portion defining a long axis, and wherein the floatingmember is capable of moving as a unit transversely to the long axisduring movement of the first bone with respect to the second bone and/orthird bone after the step of installing.

C5. The method of any of paragraphs C1 to C4, wherein the floatingmember is capable of moving translationally during movement of the firstbone with respect to the second bone and/or third bone after the step ofinstalling.

C6. The method of any of paragraphs C1 to C5, wherein the floatingmember is rotatable with respect to the fixed member during movement ofthe first bone with respect to the second bone and/or third bone afterthe step of installing.

C7. The method of any of paragraphs C1 to C6, wherein the prosthesisincludes a head portion that includes the fixed member and the floatingmember, and wherein the head portion includes at least one resilientmember that is deformable to bias a position of the floating member withrespect to the fixed member.

C8. A method of replacing an end of a bone with a prosthesis having astem portion and a head portion, the method comprising: installing theprosthesis in an operative configuration, with the stem portion mountedto a first bone, a first member of the head portion articulating with asecond bone, a second member of the head portion articulating with athird bone, and the second member movably connected to the first member.

C9. A method of replacing an end of a bone, the method comprising:installing a prosthesis, with a stem portion thereof mounted to a firstbone and an articular member of the prosthesis articulating with asecond bone and operatively connected to the stem portion such that thearticular member is permitted to float as a unit transversely to a longaxis defined by the stem portion.

C10. The method of paragraph C9, wherein the articular member isrotatable with respect to the stem portion.

C11. The method of paragraph C9, wherein the articular memberarticulates with a second bone and a third bone.

C12. The method of any of paragraphs C9 to C11, wherein the articularmember is operatively connected to the stem portion by a movable jointincluding a spherical surface region forming less than one-half of acomplete sphere.

D1. A device for replacing an end of a bone, comprising: (i) a stemportion that mounts to a first bone; and (ii) a head portion operativelyconnected or connectable to the stem portion and including a fixedmember to articulate with second bone and a floating member toarticulate with a third bone.

E1. A device for replacing an end of a bone, comprising: (i) a stemportion that mounts to a first bone; and (ii) a head portion operativelyconnected or connectable to the stem portion and including a firstmember to articulate with a second bone and a second member toarticulate with a third bone, the second member being movably connectedto the first member when the head portion is operatively connected tothe stem portion.

F1. A device for replacing an end of a bone, comprising: (i) a stemportion that mounts to a first bone; and (ii) a head portion includingan articular member for articulation with a second bone, the headportion being operatively connected or connectable to the stem portionsuch that the articular member is permitted to float as a unit relativeto the stem portion and transversely to a long axis defined by the stemportion.

F2. The device of paragraph F1, wherein the articular member isconfigured to articulate with a third bone.

The disclosure set forth above may encompass multiple distinctinventions with independent utility. Although each of these inventionshas been disclosed in its preferred form(s), the specific embodimentsthereof as disclosed and illustrated herein are not to be considered ina limiting sense, because numerous variations are possible. The subjectmatter of the inventions includes all novel and nonobvious combinationsand subcombinations of the various elements, features, functions, and/orproperties disclosed herein. The following claims particularly point outcertain combinations and subcombinations regarded as novel andnonobvious. Inventions embodied in other combinations andsubcombinations of features, functions, elements, and/or properties maybe claimed in applications claiming priority from this or a relatedapplication. Such claims, whether directed to a different invention orto the same invention, and whether broader, narrower, equal, ordifferent in scope to the original claims, also are regarded as includedwithin the subject matter of the inventions of the present disclosure.Further, ordinal indicators, such as first, second, or third, foridentified elements are used to distinguish between the elements, and donot indicate a particular position or order of such elements, unlessotherwise specifically stated.

We claim:
 1. A method of replacing an end of a radial bone with a radialhead prosthesis having a stem portion and a head portion, the headportion connected or connectable to the stem portion, the head portioncomprising a fixed member and a floating articular member, the methodcomprising: operatively installing the prosthesis such that the stemportion of the prosthesis is attached to a radial bone, the fixed memberdirectly articulates with an ulnar bone, and the floating articularmember directly articulates with a humeral bone and is operativelymovable translationally with respect to the fixed member in a directiontransverse to a long axis defined by the radial bone when the radialhead prosthesis is finally implanted and fully operational, wherein thefixed member includes a cup portion, and wherein the floating articularmember is disposed in the cup portion after the step of installing. 2.The method of claim 1, wherein at least one of the ulnar bone and thehumeral bone includes a prosthetic region, and wherein at least one ofthe fixed member and the floating member articulates at least in partwith a prosthetic region.
 3. The method of claim 1, wherein a majorityby volume of the floating member is disposed in the cup portion afterthe step of installing.
 4. The method of claim 1, wherein the floatingmember is rotatable with respect to the fixed member during movement ofthe radial bone with respect to the ulnar bone and/or humeral bone afterthe step of operatively installing.
 5. The method of claim 1, whereinwherein the head portion includes at least one resilient member that isdeformable to bias a position of the floating member with respect to thefixed member.
 6. A method of replacing a proximal end of a radial bonewith a radial head prosthesis having a stem portion and a head portion,the head portion connected or connectable to the stem portion, themethod comprising: installing the prosthesis in an operativeconfiguration, with the stem portion mounted to a radial bone, a firstmember of the head portion directly articulating with an ulnar bone andfixed with respect to the stem portion, and a second member of the headportion directly articulating with a humeral bone and operativelymovable translationally with respect to the first member in a directiontransverse to a long axis defined by the stem portion when the radialhead prosthesis is finally implanted and fully operational, wherein thesecond member is a floating articular member, wherein the first memberincludes a cup portion, and wherein the floating articular member isdisposed in the cup portion after the step of installing.
 7. The methodof claim 6, wherein the second member is rotatable with respect to thefirst member in the operative configuration.
 8. The method of claim 6,wherein at least one of the ulnar bone and the humeral bone includes aprosthetic region, and wherein at least one of the first member and thesecond member articulates at least in part with said prosthetic region.9. The method of claim 6, wherein the second member is connected to thefirst member by a movable joint that permits translational motion androtational motion of the first and second members relative to eachother.
 10. The method of claim 6, wherein the second member is connectedto the stem portion by a slidable joint and a pivotable joint that aredistinct from each other.
 11. The method of claim 6, wherein the step ofinstalling permits the floating articular member to rotate as a unitwith respect to the stem portion to change a tilt of the floatingarticular member with respect to the stem portion.
 12. The method ofclaim 6, wherein the floating articular member is operatively connectedto the stem portion by a movable joint including a spherical surfaceregion corresponding to no more than one-half of a complete sphere.